1. Field of the Invention
The present invention relates to a fingerprint sensor and a fingerprint sensing method; in particular, to a fingerprint sensor and a fingerprint sensing method that can improve the defocusing of electric field distribution.
2. Description of Related Art
In recent years, mobile devices have been widely used by people. Particularly, those personal mobile devices having touch panels have become an essential tool in our daily life and at work. To comply with safety requirements, those personal mobile devices are usually installed with a code locking process, and the codes could be numbers, patterns or biometric features, such as fingerprints.
In terms of personal mobile devices using the fingerprint sensing technology, the sensibility of the fingerprint sensors is limited and restricted by the thickness of each structure layer which covers upon the sensing electrodes, such as the protection layer of the touch panel of the mobile device, because of the defocusing of the distribution of electric field.
Please refer to FIG. 1. FIG. 1 shows a schematic diagram of a conventional fingerprint sensor according to the prior art. In the prior art, applying electric fields at both sides of the sensing electrode to improve the defocusing of the distribution of electric field is common. As shown in FIG. 1, the electric field E is applied at the left side and the right side of the sensing electrode S such that the distribution of the electric field would tend to converge to the central part which makes the electric signals transmit for a longer distance. However, as known by those skilled in the art, the sum of the thickness of layers that the electric signals can transmit through is still limited.